Manufacturing quality printed circuit boards using thermal transfer paper using the loot method. Paper for making printed circuit boards using LUT technology or how to make a printed circuit board at home Choosing paper for loot

In this study, I tried to find the real limits of LUT application, find out what are the minimum gaps and paths and decide on the best paper for the process. The practical goal is to achieve the cherished 0.1mm, which, as some say, can be made with LUT.

Note: all photos are very high resolution from 300KB to 4MB in size so that all the details are visible. Therefore, I did not insert them into the text, but I give links to them.

General process

I will not go into theory, but simply describe on what and what I do in my home environment.

Sprint Layout program, I print on HP LaserJet 1200 (600dpi), foil textolite 1.5 mm thick, one-sided, small iron, travel iron, etching with ferric chloride, toner I erase with solvent 646.

Before printing, I sand the board with sandpaper 1000 and wipe it with 646th solvent.

Paper selection

Paper selection criteria:

• availability
• good toner coverage and print adhesion
• good transfer of toner to the board from paper
• ease of removal from the board after toner transfer
• coating (or mixing) the toner with a layer that closes the pores in it.

The last point requires clarification. The bottom line is that all LUT technology is based on laser printing, and any laser printing on toner, and any toner suitable for LUT suffers from one very unpleasant drawback: porosity. Because of this, strong undergrazing of the tracks occurs, even with a not very long etching time. And most importantly, there is an etching of large surfaces that are covered with toner. They seem to be eaten away from above, sometimes through and through. Photo paper, in particular, has a pseudo photo layer that can mix with toner at high temperatures, covering it with an impenetrable plastic-like film that is resistant to etching. However, according to the experience of other amateurs, this layer often also fits tightly on the board and is difficult to peel off, or clogs into the gaps, which makes it difficult or impossible to make small gaps. Abroad there is a commercial solution to this problem - the GreenTRF folk. Who cares - read Google.

From the very beginning, I tried 80g / m2 regular office paper. Complete nonsense. Does not release toner.

Then he did it on the pages of glossy magazines. It turns out pretty good, but you need to soak for a long time, the transfer of toner to the board is not complete, the toner spreads strongly when heated with an iron.

HP Branded Inkjet Matte Photo Paper. The toner is poorly transferred to the card, not, the toner is not covered with anything on top, it remains porous.

HP Semi-gloss Photo Paper. After 30 minutes of soaking, it is impossible to remove the paper from the board. All toner is coated with white plastic. You can only tear off with toner.

Thermal transfer paper for inkjet printers for transferring to clothing. I was afraid to shove it into the laser - it painfully melts easily. I wanted to melt the toner aors. Complete failure.

It would seem that everything was lost. There is no way out, try the same thing from other firms (still a lot of money down the drain) or change hands.

But here's what Thomas Edison said:

"Too many people break down without even knowing how close to success they were at the moment they lost heart."

And he was very right!

After all this torment, I went to read about GreenTRF, about commercial systems for LUT, how they work, I tried to understand and when I read about press "n" peel I read that the temperature there should not be very high (as for polyester). And I thought maybe I was overheated.

I put the iron between 1 and 2 dots and used the same photo paper from HP Premium, which stuck tightly. He warmed up for 3 minutes, went to the bathroom, turned on cold water and tugged at the paper. She walked away without any resistance at all! About 90 percent of the pattern remains on the copper! And very black. There is almost no toner on paper!

After 3 tests, I found that it is optimal - one division above 2 points (there are still a lot of divisions on my iron between the points). In this case, the back of the paper is already starting to melt, so you need to put 1 sheet of plain paper. I tested on a small scarf, so there was no need to drive the iron back and forth, however, I pressed normally and sometimes passed along the contour with little pressure. Warm-up: 3.5-4 minutes.

After that, I immediately take it by the piece of paper, go to the bathroom, put it under cold water and after 3 seconds I remove the paper with one movement. Here's what happens:
/elektro/tt/IMG_3517.jpg

Where there was toner, the paper becomes bluish, and the toner on the card feels like plastic, shiny and glossy. However, there is no photolayer anywhere in the cracks! There is nothing to scratch out! By the way, the paper is very interesting; when it gets wet from the gloss side, it becomes covered with some kind of slippery gruel, like real photographic paper. As you can see, the toner has gone perfectly! Beauty!

My LaserJet 1200 swallows both a full 10x15 sheet and a half 10x7.

Method of measurement

The method is simple: we take a camera, a ruler and an object, put the ruler on top of or next to the object and take a large macro shot. We count the number of pixels in 1 mm on the ruler, count the number of pixels on the object, divide the latter by the first and get the size of the object in pixels.

For those. who doubts this measurement technology, I conducted an accuracy test. I have a chip from TI psp54310pwp in a very small package. According to the datasheet, his leg is 0.19 mm thick, and the distance between the middle of the legs is 0.65 mm. By my method, after photographing the chip, the values ​​obtained are: 0.20 and 0.62, respectively. So, I think there will be no question about accuracy.
/elektro/tt/4/IMG_3532.jpg

Testing for track thickness and gaps

After that, I made a bath with ferric chloride more abruptly. I etched everything in 15 minutes. Here's the result:
/elektro/tt/IMG_3518.jpg

Looks great. All tracks came out completely (even 0.05mm), the gap of 0.1 did not come out at all (but no one hoped), but 0.2 is completely intact.

I use a multimeter to test all the tracks - all intact. Testing the clearances. Oops, 0.2mm conducts! Here you can see the place where there is a bridge:
/elektro/tt/IMG_3521.jpg
(circled in red)

One movement of the needle over this area and the problem is fixed.

But the question is, what are the real dimensions?

As before, we apply a ruler and take a macro photo:
/elektro/tt/IMG_3521.jpg

And we get: 1 mm: 30 pixels

Tracks:

• 0.05mm 5px 0.17mm
• 0.10mm 7px 0.23mm
• 0.15mm 9px 0.30mm
• 0.20mm 10px 0.33mm

Sadly. And the paper is super, and the hands are not hooks, like. But it doesn't go less than 0.17! I did the maximum filling with toner when printing (this is when the printer is told that printing on a transparent film), maybe if it's not so greasy to do, then the toner will not creep out so much when melted with an iron.

Clearances

• 0.2mm 6px 0.2mm
• 0.3mm 9px 0.3mm
• 0.4mm 13px 0.43mm

The gaps, for some reason, came out perfectly!

In general, it turns out very nicely, but the tracks, alas, are not of the same size.

By the way, about the laser printer itself. My maximum is 600dpi. Those. 236 lines per 1 cm. 24 lines at 0.1mm. It seems to me that at such sizes, the errors are already prohibitive for this printer. Especially with a recharged cartridge and a stale drum and no one knows what toner.

Who knows how much toner floats when printing? Let's carry out a simple experiment. We print the same layout in normal mode on paper and see how thick they are on paper, even before transferring.

We carry out 4 experiments, the scale is a caliper (to be more precise):

• bold printing on photo paper
• plain printing on photo paper
• normal printing on plain A4 paper (after passing through the printer several times)
• control measurement of the just made board.

We measure only track 0.1. The method is the same as described below (1mm in pixels is determined in each frame separately)

1. bold printing on photo paper
   /elektro/tt/3/IMG_3524.jpg
   by 1 mm - 34 p.
   track 0.1 - 6p. - 0.17 mm
2. plain printing on photo paper
   /elektro/tt/3/IMG_3525.jpg
   1 mm - 35 p.
   track 0.1 - 5p. - 0.15 mm
3. Plain printing on plain A4 paper
   /elektro/tt/3/IMG_3526.jpg
   1 mm - 35 p.
   track 0.1 - 5p. - 0.15 mm
4. control measurement of the just made board
   /elektro/tt/3/IMG_3527.jpg
   1 mm - 35 p.
   track 0.1 - 7p. - 0.2 mm

In this light, I have a question: what paths of 0.1mm can we talk about, if the print itself is ALREADY thicker, and there will still be a melt during transfer? It is stupid to hope that they will be pushed to the desired width, since then the gaps will be pushed and there will be problems.

Could there be a problem with the printer? Maybe 600dpi is not enough? In the office, a test drawing was printed on a 1200 dpi printer (HP LJ 3055) on plain paper (80g / m2) and on the same HP Premium Photo Paper, and the dimensions of the drawing were measured at home.

The measurement was made only along the 0.1 track (just taken as a reference, so as not to suffer too much).

Photo paper: 0.125mm
Plain paper: 0.11mm

Not bad, yes. Not that at home at 600dpi. However, there is clearly a different toner, does not sit well on photo paper. A lot of "hairiness". Tracks 0.05 are visually printed with tears on photographic paper, but measurement showed that there is a size of 0.09mm.

We translate to copper.

So, the size on the copper track is 0.1mm - 0.17mm

I etched it in a steep solution, everything went away in 10 minutes.
/elektro/tt/4/IMG_3538.jpg
(there are subgrads, with home at 600dpi there is no such thing, in places the toner of tears is just, strange)

The resulting track size is 0.1mm - one 0.18mm and the second 0.20 (for some reason, different ones came out).

The track size is 0.05mm - 0.15mm, but it is terribly uneven, one track is torn in the middle.

The electrical test failed one track 0.05mm (well, which is 0.15 in fact) and the gap 0.2 closed too. After I went through the gap with a paper knife, everything went.

Conclusion: 1200 dpi does not help, and the toner is less suitable there.

So, a new test pattern:
/elektro/tt/4/IMG_3534.jpg

Places are marked where the toner simply did not take on the paper, until I understand exactly why this sometimes happens, but it depends on how to turn on the water from the tap and when to pull the paper, it is better to put water right into the knock between the board and the paper.

It adds footprints for SMD.

One has a contact width of 0.44 mm, a gap of 0.17 mm.
Second: the contact width according to the scheme is 0.63mm, the gap is 0.62mm.
/elektro/tt/4/IMG_3544.jpg
At the top right, there is still a place for an SMD capacitor of size 0402 (the frame is a silk screen type.

I take the mentioned HP photo paper, my printer with 600dpi. I am typing.

Dimensions on paper:

• 0.63mm - 0.63mm
• 0.44mm - 0.43mm
• 0.1mm - 0.14 (already swam)

Resulting dimensions on boards after etching:

• 0.63mm - 0.65mm
• 0.44mm - 0.43mm
• 0.1 mm - 0.22 mm
• 0.05mm - 0.18mm

And don't ask me why the 0.43 didn't float. Maybe it's some special size that the printer can print correctly and some kind of melting force holds the toner together.

It's nice that the tracks are smooth, without gouging.

The electrical test showed that all the tracks are intact, and there is a short circuit in the gap 0.2. One connection in one place. I removed it with a knife - no problem.

Of 4 cases, in 100% in the gap, 0.2 closes and in 100% it is treated with one pass of a knife or needle. Probably better to do it then etching.

Checking the places for the SMD showed that there are no short circuits at all. Since the size of the platform is respected, the clearances are also respected. Those. there are gaps of about 0.17mm without short circuits. And don't ask why - I don't know!

conclusions

1. HP Premium Photo Paper (Q199HF) rules over black!
2. If translates toner with a laminator, then you need a laminator ALWAYS with temperature control!
3. You need to poison quickly! The longer you poison, the more sub-herb.
4. The temperature on the iron must be selected individually for the iron, toner, paper, and, possibly, the board (for this paper, you need to find the minimum at which all the toner passes after 4-5 minutes of warming up).
5. The limit of technology with a printer at 600dpi and Chinese toner in a recharged cartridge is 0.18mm
6. To get the track 0.18-0.20, you need to draw 0.05-0.20 in the scheme! It is very important!

I think the theme with 0.1mm tracks can be closed. There are no such tracks on LUT and there cannot be! But what there is is quite enough to make TQPF144 for AVR32 without any special problems, we can even say that it is without any problems at all (pad 0.25, gap 0.25 and everything is ok, there is a step of 0.5mm).

If someone thinks that they have actually made a 0.1mm track with LUT, I’m waiting for a macro photo with the attached ruler, and we will laugh together.

Some far-reaching conclusions

Glossy photographic paper absorbs anyway better than transparencies. The photo method uses a transparent film over the resist. On this film, the thickness cannot be less than on glossy photo paper, i.e. we are talking about a minimum of 0.15mm. Further, when illuminated, shadowing or highlighting of the tracks may occur, due to which they can be thicker or thinner, and significantly in the ratio of 0.15 mm (i.e., for example, they can move from 0.1 mm to 0.2 mm). In addition, the experience with the 0.09 track showed that it is easily etched and even gnawed in places by the etching composition. This is all theory, since I have never used the photo method, but it seems to me that there is a limit of about 0.15mm. If someone thinks that they have done less - macro photo with a ruler in the studio.

ATTENTION! ATTENTION! ATTENTION! ATTENTION!

Later it turned out that the specified HP Premium paper is absolutely not suitable for the manufacture of boards larger than 3 by 5 cm, since when the paper is removed, scraps of toner are torn out. Read the next section for information on the correct paper. Second part .

ATTENTION! ATTENTION! ATTENTION! ATTENTION!

Quite many years ago, I first learned about the manufacture of boards using Laser Iron Technology. For me it was like reinventing the wheel.
Read the continuation of the story under the cut.

Prior to this, the boards were painted with varnish using a reedfeder. To print circuit boards using LUT technology, I even bought a laser printer (12 years ago it was very expensive). In the process, I tried a bunch of different types of paper. And more than one square meter of boards made using this technology was made, on the third I stopped counting. At the moment, I settled on paper from the magazine Popular Mechanics, before that I used paper from the magazine Kitchens and Bathrooms, but it disappeared from sale.
But more recently, while reading reviews on Muska, I accidentally saw paper for printing boards in one of the reviews, climbed on Ali and immediately ordered myself a trial 10 pieces of leaves, deciding that if I liked it, I would order 50, since the price difference is between 10 and 50 only about two times.
By the way, be careful, I posted a link to the lot, but now at this place there is a lot of 50 pieces for 10-plus bucks, while the name of the link remains the same, 10 sheets.

I recently received my order. What I was most afraid of happened, the paper came wrinkled.
As everyone understands, it is dangerous to put crumpled paper in a printer; the cost of repairs may be more than the cost of the paper itself. I opened a dispute for a 50% refund, since after pruning I can use about that much.

The paper was just in a large envelope, without a bag or file, and a piece of some kind of cardboard was laid, and this piece of cardboard was smaller in size than the paper. Actually, the main damage was in places where the cardboard was missing.

In the photo, the magazine that I used before and the paper I received, chose the leaf more carefully.

To prevent the printer from chewing on my new leaf, I had to cut off part of it, on the other hand I did not cut it off, since it is not critical there, the main thing in that area is simply not to print anything.

Well, since such paper is well, a very specific product, then without testing, there is simply no way.

In general, everyone who is interested is welcome under the spoiler.

Printed circuit board, how it's done.

First I trace printed circuit board, I use Sprint Layout 6, before that I used version 3 for a very long time, and I still can't get used to the differences in control.

When making a board, I always leave a protective zone with a width of 5mm around the perimeter, so the workpiece is taken 10mm more in length and width than the required board, it is so convenient for me.

The workpiece is cleaned with fine sandpaper, it is not the mirror surface that is important, but rather a lot of micro-scratches, then the toner holds better.

We print our future board on paper (I usually print 2 pieces at once, just in case), on the smooth side, by the way, the whole process was done with one take, i.e. I did not correct or alter anything specifically for the review, this was the point of the test.
Do not forget that you need to print in a mirror image in relation to the required printed circuit board pattern.

Then I put the blank on a specially trained book :), or rather, this is not a book, but an annual filing of Radio magazines, in a cardboard binding. I do this so that the workpiece does not slip in the process, and does not spoil what is under it from heating.

After that, I lay the printout with a drawing to the copper, then cover it on top with a sheet of ordinary printer paper, so it slips less at the initial stage, the most difficult moment is to prevent the printed sheet from sliding to the side, I first put the iron with its wide part on the book and paper, and then smoothly I lower it onto the workpiece.

Then, with smooth movements, with a slight pressure, we stroke our future board, I make several passes from different sides of the board, so that the edges are better ironed, you cannot press hard, otherwise the toner may float, if you do not press at all, then most likely the toner will not stick to the workpiece. I iron this workpiece for about a minute.
By the way, I use Static Control toner, in my opinion this is the best toner for LUT ...

The gluing process is complete, the paper adhered smoothly and beautifully.

Now we throw our board into a bowl of water for 5-10 minutes, you can leave the water on, this will help the paper become softer faster.

After 5-10 minutes, under a slight pressure of water (better than room temperature), roll up the paper with your finger, the tracks should remain in place, you do not need to do this too carefully, since if the toner is erased with a finger, then such a board needs to be redone, normally glued toner cannot be erased with a finger , only scratches.

The photo shows the result of transferring the drawing to fiberglass. Toner is black, before that when I used paper from a magazine, the toner had a grayish tint, as there were particles of paper on it. Everything here is beautiful, the holes are clean, there are no sticks between the tracks.
I specially selected for the test a printed circuit board with both large filled polygons and small tracks.

Before etching, I make such a "table", in the corners of the board, in places free from the drawing, I drill 4 holes into which I insert matches (or toothpicks), the board is positioned with the drawing down.

The boards are usually etched with a solution of ferric chloride in water.
(III)
After immersing the board in the solution, it must be lifted almost immediately and air bubbles removed, otherwise there will be no etched places.

After a while (depending on the solution), the board is etched.

I wash off the toner that has already fulfilled its function with acetone (well, or any suitable solvent).

Well, here I will show what kind of print quality I got in the end.
The place for the processor is closer to the center of the board, the width of the contact pads is 0.45mm, the width of the tracks is 0.45-0.5mm. It can be seen that even the shape of the pad is perfectly preserved.

And this is a path along the edge of the board, there are two such places. Usually I correct such places with a permanent waterproof marker, for the test I did not do this on purpose.

After washing off the toner, I drill the necessary holes, then I clean the board with zero sandpaper.

After all these operations, I only cut off the excess, if this is done before stripping, then it is possible to damage the tracks close to the edge of the board with sandpaper. I pass the edges of the board a little with a file to remove the sharp remnants of fiberglass after the scissors.

Now I cover the board with flux (I use alcohol F3), and plunge the tracks.
I know some people don't, but I like the board with spilled tracks better. In general, a matter of taste, well, copper does not oxidize, and microcracks are filled with solder.

The last stage, I wash off the remnants of the flux with acetone.

That's it, the board is ready.

Yes, I know about photography, I know about masking and silk-screening, etc. etc.
These are all good and very useful things, but I think that the option I described is sufficient for most applications. Making a board this way is very quick and easy, and you need to have a minimum of chemicals and tools.
The board I made will probably take part in one of my future reviews, some readers will most likely even find out what kind of device it will be.

In general, my resume.
Pros.
I liked it, I think I will order 50 or 100 sheets.
Toner sticks well to the substrate.

Minuses.
The seller packaged very badly, for which he was a big minus.
The price, especially the price when buying a lot of 10 leaves, but for a sample is quite enough, although looking for magazines, and then leaves in magazines without pictures (for printing it is better to use either white pages or only with text) is already tired of the order.

In general, experts, do not judge strictly, I tried to describe as best I could, I will be very glad to advice and additions, and I hope that my review helped someone.
And yes, I know that it is cheaper on BiK :)))